JP4449135B2 - Semiconductor substrate holding container - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
This invention adheres to the surface of a semiconductor substrate (also referred to as a wafer) out of trace impurities present in cleaning ultrapure water (evaluated water) used in large quantities in LSI manufacturing processes, etc. The present invention relates to a holding substrate for a semiconductor substrate used for evaluating the quality of ultrapure water with high sensitivity only for substances that may adversely affect the characteristics of the semiconductor.
[0002]
[Prior art]
Since ultrapure water used in large quantities in the LSI manufacturing process is a substance that comes into contact with the wafer at the end of the cleaning process, the concentration of impurities contained in the ultrapure water has a degree of cleaning of the surface of the wafer such as silicon. Affects. For this reason, it is necessary to reduce the impurity concentration in the ultrapure water used in the manufacturing process along with the increase in LSI integration so far, and conventionally, all impurities contained in the ultrapure water are reduced. Efforts to reduce have been made. For this reason, the development of a technique that can analyze impurities in water to ultra trace amounts using a highly sensitive analyzer has been performed.
[0003]
However, considering the adverse effects of impurities in the ultrapure water on the substrate, the substances that have an adverse effect first attach to the wafer surface from the water, and then cause diffusion and chemical reactions when processing such as heating. It can be considered to cause adverse effects. That is, all substances that have an adverse effect in ultrapure water are included in substances that adhere to the wafer surface from the water. Therefore, without analyzing every impurity in the water and evaluating the water quality, the substrate made of the same material as the object to be cleaned is brought into contact with the ultrapure water to be used, and the target impurity is adhered to the surface of the substrate. If the impurities attached to the substrate are analyzed using a technique for analyzing impurities on the surface of the substrate, only impurities that have the property of attaching to the substrate surface from ultrapure water, in other words, that may have an adverse effect, are detected. Thus, the quality of ultrapure water can be evaluated. For this purpose, hold a silicon wafer in a sealed container, introduce ultrapure water into the container, and contact the wafer with ultrapure water for a certain period of time, then take out the wafer and analyze the surface impurities by an appropriate method. Has been done. As a contact method for this purpose, the container used for cleaning the wafer is usually filled with ultrapure water, and the wafer is immersed in the ultrapure water and brought into contact with the ultrapure water, or the container is filled with ultrapure water. There is a method in which a wafer stored in a cassette in a container is immersed and contacted with ultrapure water in a container while water is continuously supplied.
[0004]
[Problems to be solved by the invention]
However, this method can be operated only in a highly clean environment such as an LSI manufacturing environment because the wafer contacts the ambient air before and after the cassette containing the wafer is immersed in ultrapure water. . Impurities are considered to move from the water in the vicinity of the wafer surface to the surface of the wafer, and it is considered that the lower the concentration of the water passing through the vicinity of the wafer, the lower the concentration of impurities can be detected. In the method of immersing the wafer in water, the flow rate of water flowing in the vicinity of the wafer is small, so that the amount of water in contact with the wafer is small. If it is immersed for a long time in order to increase this, the amount of water to be used becomes extremely large, which causes a practical problem. In addition, when a cassette containing a plurality of wafers is immersed in water in a container and test water is supplied, it is impossible to keep the flow rate of water flowing near the surface of the wafer constant for any substrate. The amount of adhering also becomes uneven.
[0005]
[Means for Solving the Problems]
The present invention has been developed to solve the above-described problems, and the container for holding a semiconductor substrate according to claim 1 is subjected to analysis by analyzing the surface of the semiconductor substrate after contacting the semiconductor substrate with water to be evaluated. It is used in a water quality evaluation method for detecting or measuring impurities in evaluation water , and has a holding means for holding and horizontally holding one semiconductor substrate inside, and the evaluation water is placed on the surface of the semiconductor substrate. A water supply port for water to be evaluated is supplied to the central portion and flows outward in the radial direction toward the outer periphery thereof, and a water discharge port for discharging the water to be evaluated from the outer periphery of the substrate through the back surface thereof. An upper lid having the water supply opening at the center and a circular depression having an upper end of the drain opening at the center of the bottom of the depression on the upper surface, and the circular depression is closed by the upper lid. A bottom plate that can be peeled off, and A plurality of radial ridges are provided at equal intervals in the circumferential direction on the bottom surface of each of the ridges, and each of the ridges has an inner end positioned around the drain outlet and an outer end inward from the inner peripheral surface of the recess. A holding substrate for a semiconductor substrate according to claim 2, wherein a stepped support base having a step that is spaced apart and is held horizontally by placing a peripheral portion of the semiconductor substrate horizontally is provided . 2. The holding substrate for a semiconductor substrate according to claim 1, wherein the distance between the surface of the semiconductor substrate and the inner surface of the container facing the surface is shortened as the distance from the central portion of the semiconductor substrate toward the outer periphery changes in the radial direction. According to a third aspect of the present invention, there is provided the semiconductor substrate holding container according to any one of the first and second aspects, wherein the material of the liquid contact portion of the container is an acrylic resin. , Polyvinyl chloride, polyp 5. Holding a semiconductor substrate according to claim 4, characterized in that it is a thermoplastic synthetic resin such as pyrene, polyethylene, tetrafluoroethylene, perfluoroalkoxy resin, poly (vinylidene fluoride) resin, polyether, ether ketone, polyphenylene sulfide. The container is a semiconductor substrate holding container according to any one of claims 1 and 2, wherein the material of the liquid contact portion of the container is stainless steel, aluminum, or quartz.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an embodiment of a semiconductor holding container according to the present invention. The container includes an upper lid 10 and a bottom plate 20 in which a circular recess 21 on the upper surface is closed by the upper lid. The outer shape of the upper lid 10 and the bottom board 20 is circular, for example, and a water supply port 11 is opened at the center of the upper lid, and a drain outlet 22 is opened at the center of the bottom board 20. Positioning projections 23 are provided at equal intervals in the circumferential direction on the peripheral portion of the upper surface of the bottom plate 20, and correspondingly, recesses for receiving the positioning projections are provided on the peripheral portion of the lower surface of the upper lid. Accordingly, when the upper lid is placed on the upper surface of the bottom plate and the concave portion of the upper lid is fitted into the positioning projection 23, the upper lid correctly overlaps the bottom plate and closes the upper surface of the circular recess 21 of the bottom plate.
[0007]
The inner diameter of the circular recess 21 in the bottom plate is sufficiently larger than the diameter of the wafer W to be held, and the upper end of the drain port 22 is opened at the center of the bottom of the recess. On the bottom surface of the recess 21, a plurality of, in the drawing, three radial rods 24 are provided at regular intervals in the circumferential direction. The inner end of the radial trough 24 is located around the drain port 22, and the outer end is spaced apart from the inner peripheral surface of the recess 21 inward.
[0008]
The wafer W is held horizontally on the plurality of radial ridges 24. Therefore, a step-shaped support base 25 having a step 26 on which the peripheral edge of the wafer is placed is provided on the outer end portion of each ridge. The level difference of the level 26 corresponds to the thickness of the wafer (about 0.6 mm). Further, if necessary, a support portion 27 for supporting the lower surface in the radial direction of the wafer is provided on the intermediate portion of each flange 24.
[0009]
On the lower surface of the upper lid 10, there is provided a Mt. Fuji water passage recess 12 that is continuous with the lower end of the water supply port 11. The inner diameter of the water recess 12 is equal to the inner diameter of the circular recess 21 in the bottom plate. The concave portion 12 for passing water is referred to as “Mount Fuji” so that in the cross-sectional shape, the lower surface of the concave portion 12 is outward in the radial direction and gradually approaches the upper surface of the wafer W supported horizontally on the stepped support base 25. It is.
[0010]
For example, when the radius of the wafer is 75 mm, the distance of the water recess 12 from the top surface of the horizontally supported wafer is 15 mm at a position 5 mm radially outward from the center of the wafer, and 7 at a position 10 mm. .5mm, 5mm at 15mm, 3.75mm at 20mm, 2.5mm at 30mm, 1.875mm at 40mm, 1.25mm at 60mm, 1mm at 75mm on the outer circumference is there. This is because ultrapure water supplied from the water supply port 11 flows on the upper surface of the wafer W radially outward at a uniform flow rate and flow velocity, and between the inner peripheral surface of the recess and the outer end of the radial ridge. It reaches the peripheral edge portion 21 'at the bottom of the recess including the interval. This
(1) The amount of contact water can be controlled even during repeated tests, and evaluation with high reproducibility can be performed. And since the supplied water contacts a wafer efficiently, a large amount of water can be contacted with a wafer even for a short time, and the sensitivity is high.
(2) Since the flow velocity of water flowing on the surface of the substrate is uniform, the adhesion of impurities to the wafer becomes uniform, and the reliability of deposit evaluation by surface analysis is high.
{Circle around (3)} Also, when water comes into contact with the wafer, the elution of impurities from the wafer is extremely small, so that the amount of contamination of the wafer from the supplied water can be detected with high sensitivity.
There is an effect.
[0011]
The water that has reached the peripheral edge 21 ′ of the bottom of the depression flows through the gap between the bottom of the depression 21 and the lower surface of the wafer lifted by the radial ridge toward the central drain 22, and from the outlet. It flows out.
[0012]
The water supply port 11 on the top lid and the drain port 22 on the bottom panel are provided with screws to shut off the outside air and the inside of the container, and when the container is carried outside the clean room, the valve is closed to prevent contact with water. Open only when implementing. It is preferable to use a three-way valve (switching between raw water → inside of the container and raw water → discharge) 13 as a valve provided in the water supply port 11. Before the container is brought into contact with water, the valve 13 can be switched from “raw water → discharge” so that water can flow without entering the container. There is an effect that it can be washed. The valve 28 provided at the drain port 22 may be a two-way valve for opening and closing.
[0013]
As the material of the upper lid 10 and the bottom board 20, when trying to evaluate metal components and ions in the test water, the synthetic resin has a low content of impurities such as metals and ions, is relatively easy to process, and is durable. Or quartz is used. In addition, in order to remove impurities adhering to the surface of the container, cleaning with heated ultrapure water or cleaning using ultrasonic waves is performed before using the container. On the other hand, when trying to evaluate the organic impurities in the test water, a metal such as stainless steel or aluminum that does not elute organic substances or quartz is used for the wetted part of the upper lid or the bottom plate.
[0014]
Example 1
Six n-type silicon wafers having a diameter of 6 inches were prepared, and the surface of the wafer was cleaned by performing normal RCA cleaning using a quartz tank. Two of them were washed and dried, and the concentration of metal element concentration (Fe) on the surface was measured using a total reflection X-ray fluorescence analyzer. As a result, the Fe concentration on the surface of the wafer after cleaning was 2 × 10 ⁹ atoms / cm ² or less.
For two of these, a silicon wafer was mounted on a polypropylene holding container having the structure shown in the drawing, and ultrapure water was passed through the water at a flow rate of 1 standing / min for 1 hour, that is, 60 standing. Thereafter, the wafer was taken out from the container so as not to be contaminated and dried, and the concentration of the metal element (iron) on the surface was measured using a total reflection fluorescent X-ray analyzer, and the average value was obtained. As a result, 5 × 10 ⁹ atoms / cm ² of iron was detected on the surface of the wafer. That is, it can be evaluated that the water causes contamination of only 5 × 10 ⁹ atoms / cm ^{2 on} average from 60 standing water.
The remaining two of the cleaned wafers are transferred to another wafer carrier and another cleaned quartz tank, and ultrapure water is poured into the quartz tank at a flow rate of 10 liters / min for 1 hour, and a total of 600 liters of ultrapure water is poured into the quartz tank. Poured into. Thereafter, the wafer was dried so as not to contaminate, and the Fe concentration on the surface was measured by the same method as described above. As a result, 3 × 10 ⁹ atoms / cm ² of Fe was detected on the wafer surface on average. That is, this water can be evaluated as water that causes contamination at 600 × 3 × 10 ⁹ atoms / cm ² .
This result shows that the contamination from water can be evaluated with a smaller amount of water by using the holding container according to the present invention to bring water into contact with the wafer.
[0015]
Example 2
Six 6-inch diameter n-type silicon wafers were prepared, and the surface of the wafer was cleaned by performing normal RCA cleaning using a quartz tank. Two of them were washed and dried, and the concentration of metal element concentration (Fe) on the surface was measured using a total reflection X-ray fluorescence analyzer. As a result, the Fe concentration on the surface of the wafer after cleaning was 2 × 10 ⁹ atoms / cm ² or less.
About two of them, a silicon wafer is mounted on a polypropylene holding container having the structure shown in FIG. 1 and transferred to the vicinity of the ultrapure water production apparatus outside the clean room, and the water at the outlet of the ultrapure water apparatus is branched. Then, ultrapure water was passed through the holding container at a flow rate of 1 standing / min for 1 hour, that is, 60 standing. Thereafter, the container was transferred into a clean room, taken out from the container and dried, and the concentration of the metal element (iron) on the surface was measured using a total reflection X-ray fluorescence analyzer to obtain an average value. As a result, 5 × 10 ⁹ atoms / cm ² of iron was detected on the surface of the wafer. That is, it can be evaluated that the water causes contamination of only 5 × 10 ⁹ atoms / cm ^{2 on} average from 60 standing water.
The remaining two of the cleaned wafers are transferred to another wafer carrier and another cleaned quartz tank, and are transferred to the vicinity of the ultrapure water production apparatus outside the clean room together with the quartz tank. A total of 600 ultrapure water was poured into the quartz tank at a flow rate of 1 hour. Thereafter, the wafer was transferred into a clean room together with the container and dried, and the Fe concentration on the surface was measured by the same method as described above. As a result, an average of 6 × 10 ⁹ atoms / cm ² Fe was detected on the surface of the wafer. This is a contamination of the wafer due to contamination in the air outside the clean room, and this method cannot evaluate the quality of ultrapure water.
From this result, by using the semiconductor substrate holding container according to the present invention, even in normal air outside the clean room, the water to be evaluated is passed through it and contacted with the wafer to evaluate contamination from water. I understand that I can do it.
[0016]
【The invention's effect】
By using the holding container of the present invention, the quality of the pure water in the ultrapure water production apparatus outside the clean room can be evaluated using a method of analyzing by contacting with the wafer, and the quality of the ultrapure water It can be used to improve ultrapure water production technology, such as improvement of cost and cost reduction.
[Brief description of the drawings]
FIG. 1A is a cross-sectional view of an embodiment of a holding container of the present invention, and FIG. 1B is a perspective view of the same base plate.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Upper lid 11 of holding container Water supply opening 12 of upper lid Water-receiving recessed part 20 of upper lid Bottom plate 21 of holding container Circular hollow 22 of bottom plate Drain port 24 of bottom plate Radial ridge 25 of bottom plate Stair-shaped support part W of radial ridge Semiconductor substrate ( Wafer)

Claims (4)

Used in a water quality evaluation method for evaluating water to detect or measure impurities in water to be evaluated by analyzing the surface of the semiconductor substrate after contacting the water to be evaluated with the semiconductor substrate, and contains one semiconductor substrate inside And holding means for holding horizontally, and supplying water to be evaluated to the central portion of the surface of the semiconductor substrate, and a water supply port for water to be evaluated for flowing the surface radially outward toward the outer periphery thereof, A semiconductor substrate holding container having a drain outlet for discharging water to be evaluated from the outer periphery of the substrate through the back surface thereof ,
An upper lid in which the water supply port is opened in the center, and a bottom plate in which a circular depression having an upper end of the drainage opening at the center of the bottom of the depression is formed on the upper surface and the circular depression is closed by the upper lid Have
The bottom plate is provided with a plurality of radial ridges at equal intervals in the circumferential direction on the bottom surface of the dent, and each ridge has an inner end located around the drain outlet and an outer end of the dent. A holding substrate for a semiconductor substrate, characterized in that it is provided with a stepped support base having a step that is spaced apart from the inner peripheral surface to the inside and that holds the peripheral portion of the semiconductor substrate and holds it horizontally. .   2. The holding substrate for a semiconductor substrate according to claim 1, wherein the distance between the surface of the semiconductor substrate and the inner surface of the container facing the surface decreases as the distance from the central portion of the semiconductor substrate toward the outer periphery changes in the radial direction. A holding container for a semiconductor substrate.   3. The semiconductor substrate holding container according to claim 1, wherein the material of the liquid contact part of the container is acrylic resin, polyvinyl chloride, polypropylene, polyethylene, tetrafluoroethylene, perfluorocarbon. A container for holding a semiconductor substrate, which is a thermoplastic synthetic resin such as an alkoxy resin, a poly (vinylidene fluoride) resin, a polyether, an ether ketone, or polyphenylene sulfide.   3. The semiconductor substrate holding container according to claim 1, wherein a material of a liquid contact portion of the container is stainless steel, aluminum, or quartz. 4.

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